This is interesting. I had the same problem: mpc would play some, but not all, avi's slowly. Audio speed and pitch was slowed as well. (For you old-timers it was analagous to playing a 45rpm record at 33-1/3 speed.) So I popped into here, did a search, and found this thread. What's weird is I don't have the registry keys mentioned earlier. It might be because I'm running WinXP SP1. In my case, I fixed it by enabling mpc's internal audio switcher (View > Options > Filters > Audio Switcher). After checking the box, I closed mpc and double-clicked on an avi that was affected by this. It played just fine. The odd thing is I had always used mpc with an external switcher and this was never a problem before.